(1) Field of the Invention
This invention relates to a modular semiconductor device comprising a plurality of integrated circuit (IC) chips mounted on a printed circuit substrate, and, more particularly, to a modular semiconductor device comprising a plurality of leadless chip carriers (LCC's) mounted on a printed circuit substrate with a high packaging density.
(2) Description of the Prior Art
Considerable advances have recently been made in increasing the integration degree of electronic components, as seen, for example, by large-scale integrated devices (LSI's). At the same time, there have been advances in increasing packaging density of electronic components.
One means to increase the packaging density is the use of LCC's. LCC's enable IC chips to be mounted thereon without conventional outer leads. As the standardized 100-mil spacing of leads is therefore no longer necessary, a 1/2 to 2/3 size reduction is possible over dual-in-line packages (DIP's), flat packages (FPP's) and other conventional IC packages.
In modular semiconductor devices comprising a plurality of LCC's mounted on printed circuit substrates, however, the high density packaging has created the problem of heat buildup. In the case where the LCC's of a modular semiconductor device are split into groups for simultaneous group selection and operation, no specific consideration has been given to the relative positioning of the LCC's. Thus, in the prior art, two or more simultaneously operable LCC's have often been juxtaposed adjacent to each other at a high packaging density in certain areas of the printed circuit substrate. This results in uneven temperature distribution over the substrate due to the heat build up. This increase in temperature of a particular area of the substrate reduces the performance and product life of IC chips in the chip carriers mounted on that area.